Direct immunofluorescence of skin biopsy: Perspective of an immunopathologist

Background: By direct immunofluorescence (DIF), presence of immune complexes in the skin biopsy at various locations such as the dermo-epidermal junction, dermal blood vessels, etc. help to arrive at a diagnosis.
Aims: (1) To study the role of DIF in confirmation or exclusion of diseases involving skin vis-à-vis histopathology and clinical diagnosis, (2) to describe the annual spectrum of dermatologic conditions that present to a tertiary referral center and require DIF examination of skin biopsy for confirmation of diagnosis.
Methods: A total of 267 biopsies received over a period of 16 months in the Department of Immunopathology were analyzed along with clinical and histopathological details and the correlation between them was studied.
Results: DIF was positive in 204 skin biopsies. Of these, 127 biopsies showed good clinico-immuno-histopathological correlation. In 10 cases, only DIF could clinch the diagnosis. In another nine cases, immune deposits were noted, which were unexpected in light of clinical and histopathological diagnosis. The most common skin involvement was seen in vasculitides. DIF was, however, non-contributory in lesions like erythema multiformè, post Kala-azar dermal leishmaniasis, sarcoidosis, lupus vulgaris, pyoderma gangrenosum and prurigo nodularis.
Conclusion: The DIF of skin in conjunction with histopathology gives the best diagnostic yield. It is invaluable in confirming the diagnosis of small vessel vasculitides and bullous lesions of skin and can be used as an additional tool to pinpoint the diagnosis of systemic and localized autoimmune diseases involving the skin.

Keywords
Direct immunofluorescence, vasculitis, immune blistering disorders of skin, lupus band test, cytoid body